1. Field of the Invention
Safety telephone is one of the commonly used emergency devices in an effort to improve safety for seniors and to promote independent living as much as possible at home, as well as in various types of nursing homes. A safety phone system comprises generally a bracelet or a necklace, provided with an alarm button. The button includes a small short-range radio transmitter for transmitting an emergency message to a base station present in the residence. The base station is connected to a telephone network and it transmits the button-sent emergency message further to a receiver. The receiver is generally an emergency exchange, which includes computer equipment for receiving alarms and messages coming from base stations over a telephone network. The alarm can also be transmitted as a voicegram or the like, for example to home attendants' mobile phones. After receiving an alarm, the receiver can place a call to the participant who has activated the alarm. The voice link can be established over the base station's speaker phone in case the participant him/herself is unable to answer the call.
2. Description of Related Art
One of the major shortcomings in available safety phone systems is that the participant is often forgetful of wearing the button, which may be a bracelet or a necklace. In a sudden emergency, for example when an elderly person falls, the alarm device is not accessible in this case. According to a British study, 27-40% of those using a safety telephone do not wear an alarm device at all or only wear it randomly [Porteus J., Brownsell S. Exploring technologies for independent living for older people, Anchor Trust, Oxon, UK, 2000, p. 60]. Thus, it can be estimated that even people in possession of a safety appliance spend in reality more than 30% of their time without the safeguard. Neither has the security service provider a possibility of monitoring use of the device, nor to make sure that clients covered by the service would indeed receive help when they need it.
Another problem results if the bracelet is used for automatic exit surveillance, for example in the case of people with dementia. In IST's Vivago system, the bracelet in possession of an elderly person, which is provided with an emergency button, functions also as an active component in exit surveillance. The bracelet transmits radio messages continuously to base stations. When a person wearing the bracelet, whose exit needs to be discovered, passes close by a base station present next to the door, the bracelet sends to the base station an identifier which is transmitted as an exit surveillance message to the receiver of alarms. It is thereby discovered that the bracelet is located in the proximity of the door. Since messages are sent by the bracelet continuously to base stations, the base station may also transmit to the receiver a disconnection message regarding the absence of bracelet-sent messages, which means that the participant has left his/her residence.
Exit surveillance is based on the supervised person wearing continuously a wirelessly communicating identifier. Thus, the receiver of alarms should also be informed in the event that the participant him/herself has removed the discussed identifier, for example unfastened the bracelet from his/her hand. If the alarm bracelet, functioning as an identifier, is not attached to the hand, exit surveillance is naturally also inoperative.
A third problem relates to wearable instruments measuring physiological signals. These include, for example, aktographs used in sleep analysis and worn around the wrist like a wristwatch, and IST's Vivago bracelet, in which aktography type measuring technology is combined with a safety alarm as described above. These instruments are used for measuring movements of the arm. In aktographs, the measurement data accumulates in the memory of a bracelet, from which it is unpacked after a test period (e.g. 2 weeks) to a PC along a cable. In the Vivago system, the measurement data is transmitted in real time wirelessly by an rf-transmitter from a bracelet to a base station, from which it can be conveyed in various ways to a measurement-data receiving PC for further analysis. The measurement data is processed in the PC for a so-called activity graph, which represents human motion activity. Generally, the activity is studied and analysed over a preceding period of several days in order to discover better for example anomalies in the participant's daily routine or quality of sleep.
If the participant disengages such a device from his/her hand, it is naturally no longer capable of measuring movements of the arm. Such occasions appear as breaks in a measuring signal, but these are impossible to distinguish from the events that the device has ceased to operate for some other reason, like as a result of the battery going flat, a technical defect or the like. If the device transmits data in a wireless manner, no data necessarily accumulates from outside the radio transmitter's range, which also appears as a break in measurement data. Having such instruments firmly attached to the hand is also important for the actual measurement. If the attachment is poor, the measuring signal shall become weaker, affecting the signal-based analysis. For these reasons, it would be highly preferential in the process of analysing measurement data to have knowledge of whether the bracelet has been attached to the hand or whether there is some other reason for the break. The problem applies generally to all wearable instruments used for measuring physiological signals. Regarding the subsequent analysis of measurement data, it is beneficial to know whether the device, and especially the sensor system, has been appropriately attached to the wearer.
The above problems can be eliminated by means of a safety device system of this invention, which has characterizing features as defined in the appended claim 1.